English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present VLA radio continuum measurements of SN1993J in M81 at thefrequencies of 0.32 (P-band), 1.3 and 1.7 (L-band), 4.9 (C-band), 8.5 (X-band),and 14.9 (U-band) GHz carried out on December 17 and 21, 2000, about 2820 daysafter the supernova explosion. We find that a power-law spectrum, free-freeabsorbed by an homogeneous, or clumpy, distribution of ionized gas yields thebest fit to the radio data. A combined homogeneous-clumpy model is not favored,but neither totally excluded. This result contrasts with the modeling of theearly ($t \lessim $230 days) radio emission from SN1993J, where a mixture ofhomogeneous and clumpy absorbers appeared to be necessary to adequatelydescribe the behavior of the light curves. The radio spectrum of supernovaSN1993J between 0.32 and 14.9 GHz is well characterized by $\alpha = -0.67 \pm0.02 $ ($S_\nu \propto \nu^\alpha$), typical of an optically thin radiosupernova. A fit to the radio spectra of SN1993J from $\sim$ 70 up to 2820 daysshows that the observed spectral index of SN1993J has been slowly evolvingsince $t\sim$1000 days on, with the observed spectral index changing from$\alpha \approx -1$ to $\alpha=-0.67$. This spectral evolution seems to suggestthat, in addition to the radiative (synchrotron) losses, adiabatic cooling andionization (Coulomb) losses at the lowest frequencies might be contributingsignificantly to the integrated electron spectrum.Comment: A&A Main Journal, in press, 6 pages. Includes minor revision

The late-time radio spectrum of SN 1993J